DESCRIPTION: (Adapted from the applicant's abstract and Specific Aims.) Inhibitors of proteolytic enzymes have multiple roles in limiting the molecular and cellular mechanisms of inflammation, which if not controlled, would result in acute and chronic lung damage. Specifically, human neutrophil elastase (HNE), and other neutrophil proteases, are controlled by plasma proteins belonging to the serine protease inhibitor (serpin) family of proteins. Inactivated or kinetically overwhelmed serpins result in unregulated proteolytic activity which often has severe and life-threatening consequences. The proposed experiments focus on the molecular biology, structural biology and biochemistry of human serpins and serine proteases in order to define the molecular interactions between these two species. Given the central role of HNE in the pathophysiology of a wide variety of lung diseases, this enzyme was chosen as the model target protease, for these studies. The Specific Aims are to determine the mechanism and structural basis of: 1) the one-to-one stoichiometry of inhibition between a serpin and HNE; 2) the rate constant of inhibition of HNE; and 3) the long-term stability of the serpin-HNE complex. The investigations proposed will utilize the high resolution crystal structure of an intact, active recombinant variant of antichymotrypsin which is an inhibitor of HNE, cathepsin G and chymotrypsin and a general kinetic scheme of serpin/enzyme reactions to guide the design and analysis of specific recombinant serpins. The three dimensional structure and biochemical properties of the newly created series of serpins will be analyzed in order to devise a structure/function algorithm that will provide a foundation on which to base a more complete understanding of the molecular properties of the serpins.